Angioplasty is a widely used procedure for treating a stenosis within a body vessel such as a human artery. During an angioplasty procedure, a medical catheter having an inflatable balloon attached to a catheter shaft is advanced within the lumen of the body vessel until the balloon is adjacent to the stenosis. Next, the balloon is inflated causing the stenosis to compress into the vessel wall and the lumen of the vessel to dilate.
Although the angioplasty procedure is generally successful in dilating the lumen of the vessel and thereby allowing increased blood flow through the vessel, often times a restenosis occurs soon after the angioplasty procedure. It is widely recognized that the bodies response (inflammation) to tissue damage that occurs during the angioplasty procedure contributes to the restenosis. Several medicaments are known to be efficacious in the prevention of a restenosis if properly delivered near the site of the inflammation.
Heretofore, a number of devices have been suggested for use in conjunction with an angioplasty procedure to obviate a restenosis. For example, one such device utilizes a balloon to position a plurality of apertures against the vessel wall near the stenosis. After positioning the apertures, a medicament is released from the apertures, where the medicament contacts the endothelium layer of the vessel. Unfortunately, use of the aperture device generally results in an insufficient amount of medicament being delivered to the target area because a large portion of the released medicament does not penetrate the vessel wall, but rather, is washed away into the blood stream. Further, due to the toxic nature of some of the medicaments used in this procedure, the large portion of medicament entering the bloodstream can cause adverse health effects to the patient.
Also heretofore, devices capable of penetrating the wall of a vessel with a dispenser and releasing a medicament within the vessel wall have been disclosed. For example, U.S. Pat. No. 5,713,863, filed on Jan. 11, 1996 and entitled “Catheter With Fluid Medication Dispensers” and which is assigned to the same assignee of the present invention, discloses such a device.
It is to be appreciated that the use of devices with expanding members and penetrating dispensers will cause some trauma to the vessel wall. Specifically, as indicated above, dilation of the vessel lumen with a balloon or other expanding member is generally known to cause tissue injury to the vessel wall. Further, penetration of the vessel wall with a dispenser will certainly cause some injury to vessel wall tissue. Finally, the release of a medicament within the vessel wall will also cause some injury to the tissue of the vessel wall.
These various forms of tissue injury will trigger an inflammation response. As indicated above, this inflammation response is widely recognized to contribute to the restenosis of the vessel. It is also known that this inflammation response will cause localized changes near the injured tissue including increased permeability and increased blood flow. This localized increase in blood flow and permeability will generally increase the dispersion rate of medicaments released near an injury in a vessel wall.
For a medicament to be effective in preventing a restenosis it must be delivered to a prescribed area and in a prescribed dosage. As indicated above, the size, shape and location of the prescribed treatment area is dependent on the amount and location of tissue injury. On the other hand, the amount of tissue injury is dependent on a number of factors including the size of the balloon, the number of penetrating dispensers and the amount of medicament released. Further, the dispersion rate of the medicament will be affected by the amount of inflammation, the type of medicament, and the amount of medicament released. Consequently, all of these factors must be considered when determining the arrangement of the dispensers and the amount of medicament to be released at each dispenser that will result in a uniform dispersion of medication at the prescribed treatment area.
In light of the above, it is an object of the present invention to provide a method useful for preventing a restenosis caused by trauma to vessel tissue from an intravascular procedure. It is another object of the present invention to provide a method for preventing a restenosis in a vessel by delivering a medicament at predetermined locations within the vessel wall for dispersion into a prescribed shape that takes advantage of the increased medicinal dispersion rate due to the localized inflammation created by the procedure. It is yet another object of the present invention to prevent a restenosis by delivering a medicament at predetermined locations within a vessel wall to create a circumferential dispersion of the medicament within the vessel wall near a stenosis. Another object of the present invention is to safely deliver dangerous medicaments into a vessel wall while minimizing the amount of medicament which is washed away into the blood stream. Still another object of the present invention is to provide a method for treating a vessel which is easy to perform, safe, relatively simple, and inexpensive to perform.